The A8509 is a multi-output white LED driver for backlighting LCD panels. It integrates a current-mode boost controller and four individual current sinks.

The boost controller architecture allows for significant scaling of boost voltage to optimize the solution for the required number of LEDs per string. The FSET/SYNC pin either sets the required boost switching frequency or synchronizes the value in the range of 300 to 800 kHz.

The LED sink current value is set by an external ISET resistor (see figure 1). The four LED sinks can also be combined to achieve even higher current per LED string.

The A8509 provides protection against output shorts and overvoltage, open or shorted LED pins, and overtemperature. A dual-level, pulse-by-pulse current limit function provides soft start and protects the external current switch against high current overloads. As an option, the A8509 can drive an external P-FET interfaced to the FAULT pin to disconnect the input supply from the system in the event of short-to-ground in the boost converter.

Package options are 24-pin TSSOP (suffix LP) and SOICW (LB) packages. The TSSOP has an exposed thermal pad, and the SOICW has four interally-fused pins, for enhanced thermal dissipation. The Both packages are lead (Pb) free, with 100% matte tin leadframe plating.

Separate Enable and PWM pins as interface for Enable and PWM Dimming functions

Fset / Sync function to either set the boost converter switching frequency or synchronize at up to 800 kHz

Protection Features

Open or shorted LED pin protection

Open Schottky protection

Pulse-by-pulse current limit

Overtemperature protection (OTP)

Package options are 24-pin TSSOP (suffix LP) and SOICW (LB) packages. The TSSOP has an exposed thermal pad, and the SOICW has four interally-fused pins, for enhanced thermal dissipation. The Both packages are lead (Pb) free, with 100% matte tin leadframe plating.

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.